This application incorporates by reference Taiwanese application Serial No. 89108056, Filed Apr. 27, 2000.
1. Field of the Invention
The invention relates in general to a transformer, and more particularly to a transformer for Liquid Crystal Display (LCD).
2. Description of the Related Art
The transformer plays an important role among various hi-tech electronic products. For example, it requires a small size transformer to energize the Cold Cathode Fluorescent Lighting (CCFL) for operating properly.
Referring to FIGS. 1A-1C, a top view, lateral view, and decomposed diagram of a conventional transformer for LCD is shown. The transformer 100 includes a U-core 102, an I-bar 106, and a bobbin 104. The U-core 102 includes inverted U-shaped bridges 108A and 108B and oblong-shaped sides 110A and 111B. The top view of the U-core 102 is a hollow rectangle and the U-core 102 is made of a high permeable material. The bobbin 104 is made of a high-voltage endurable plastic material and capable of winding the copper coil 112. The bobbin 104 further includes a number of pins 114A and 114B fixed in the Printed Circuit Board (not shown in FIGS). The I-bar 106 is a flat rectangular solid and made of high permeable material.
The stepwise sequence for assembling the transformer involves first winding the bobbin 104 with the copper coil 112 and twining the terminals of the copper coil 112 round the pins 114A and 114B for fastening. The I-bar 106 is then put into the hollow sleeve 116 of the bobbin 104 and the U-core 102 is mounted on the bobbin 104. After fixing the U-core 102, I-bar 106, and bobbin 104 together by the epoxy 118, the transformer 100 as shown in FIG. 1A is finished.
The process of producing a U-core 102 includes the following steps: a mold is first opened for the U-core 102 wherein the shapes of the mold and the U-core 102 are the same. The iron powder is filled into the mold for sintering under the pressure of injection and then shaped into the U-core 102 as shown in FIG. 1C. Since the inverted U-shaped bridges 108A and 108B of the U-core 102 are pretty thin, it fails to support the ends of the sides 110A and 110B. Therefore, the U-core 102 might be out of shape in the sintering process of manufacture. For example, the oblong-shaped sides 110A and 110B of the U-core 102 might be bent outward or bent inward.
Referring to FIG. 2, a structural diagram of a conventional mold for producing the core is shown. The traditional way to solve the aforementioned problem is making a mold shown in FIG. 2. As shown in FIG. 2, the slash part 202 is the filled portion under the bridge 108A and 108B. Utilizing the mold of FIG. 2 to shape up under the pressure of injection, it can produce an iron with the same shape of the mold. Thereafter, it won""t result in the iron out of shape during the sintering process due to its firm structure. The sintered iron then proceeds to be polished to become a U-core 102 of FIG. 1C by grinding the slash part 202. However, it is time-consuming for precision grinding and the iron is easily broken. Thus, it cost much to produce the conventional transformer.
It is therefore an object of the invention to provide a transformer with a simple structure, which is easy to be made. In no need of the step of precision grinding to shape a core, it can raise the yield of the transformer and reduce the production cost.
The invention achieves the above-identified objects by providing a transformer capable of transforming the voltage between a first port and a second port. The transformer includes a bobbin, an I-bar, the first U-core, and the second U-core. The bobbin in a tube shape has the first port and the second port wherein the first port wrapped around by at least one winding of copper coil and the second port wrapped around by at least one winding of copper coil. An I-bar made of high permeable alloy has a first end and a second end. The I-bar is inserted into the bobbin and the first end and the second end of the I-bar protrude outside the tube of the bobbin respectively. A first U-core made of high permeable alloy is placed on one side of the bobbin and has a third end and a fourth end. The third end and the fourth end of the first U-core are placed corresponding to one side of the first end and the second end of the I-bar respectively. A second U-core made of high permeable alloy is placed on the other side of the bobbin and has a fifth end and a sixth end. The fifth end and the sixth end of the second U-core placed corresponding to the other side of the first end and the second end of the I-bar respectively. Moreover, the sunken parts of the first U-core and the second U-core are in opposition to each other.